Apparatus for coating a web

ABSTRACT

A web coating apparatus employing a coating roll comprising means for feeding the web into contact with a coating roll which carries a coating material thereon, and means for blowing air against the back of the web at the position where the web is fed into contact with the surface of the coating roll.

United States Patent Kanda et a1.

[ 1 Dec. 30, 1975 APPARATUS FOR COATING A WEB Inventors: Masao Kanda, Fujinomiya; Mineo Suefuji, Minami-ashigara, both of Japan Fuji Photo Film Co., Ltd., Minami-ashigara, Japan Filed: Aug. 8, 1973 Appl. No.: 386,822

Assignee:

Foreign Application Priority Data Aug. 9, 1972 Japan 47-79745 US. Cl 118/62; 118/246 Int. C1. B05 C l/08; B05C 11/06 Field of Search 118/62, 244, 248, 246,

References Cited UNITED STATES PATENTS Stokes 118/62 X 2,408,498 10/1946 Welk 118/62 X 2,494,176 1/1950 Howard 118/247 X 2,674,974 4/1954 Gwinn et a1. 118/247 X 3,113,884 12/1963 Kohler 118/62 X 3,589,331 6/1971 Westervelt et a1 118/62 Primary Examiner-John P. McIntosh Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak 5 Claims, 10 Drawing Figures U.S. Patent Dec. 30, 1975 Sheet 1 of 3 3,929,097

US. Patent Dec. 30, 1975 Sheet 2 of 3 3,929,097

FIG. 4

U.S. Patant 136C130, 1975 Sheet3of3 3,929,097

APPARATUS FOR COATING A WEB BACKGROUND OF THE INVENTION I. Field of the Invention This invention relates to an apparatus for coating a web of paper, plastic film and the like with a coating material, which imparts various properties to the surface of the web, and, more particularly, to an apparatus for coating a flexible web with a coating material using a coating roll partially immersed in a reservoir of the coating material and partially in surface contact with the flexible web for coating the web with the material.

2. Description of the Prior Art Various types of web coating apparatus have been used in the art, and various types of web coating apparatus employing a coating roll have heretofore been put into practical use.

In coating devices of the conventional type in which the coating material is controlled in the amount transferred from the coating roll (c) to the surface of the web (a), the web can be coated with the coating material at a high speed. As the feeding speed of the web increases, however, the air flow due to the running web tends to enter between the web and the coating roll resulting a separation of the web from the surface of the coating roll. The separation of the web from the coating roll naturally causes the localized malcoating of the material on the web and the production of useless web articles without the coating layer. This malfunction of the coating apparatus particularly occurs where the web is so thin that a large tension cannot be exerted thereon or the web is slackened. However, conventional coating devices are improper for use in coating a web with a photographic emulsion or with a capsule containing material as used in a pressure-sensitive copying paper and the like which is sensitive to pressure. This is because the photographic emulsion and the capsule containing material are presensitized or broken by the pressure.

SUMMARY or THEIINVENTION In light of the foregoing description of the conventional type of the coating apparatus employing a coating roll and in view of the defects thereof, a primary object of the present invention is to provide a coating apparatus for coating a running web with a coating material by use of a coating roll in which the web is firmly put into proper contact with the coating roll at a constant soft pressure whereby the coating material is stably and uniformly transferred from the coating roll to the web at a high speed.

Another object of the present invention is to provide a coating apparatus for coating a running web with a coating material at a high speed by use of a coating roll which is suitable for coating a thin and weak web which cannot be highly tensioned.

Still another object of the present invention is to provide a coating apparatus for coating a running web with a coating material which is suitable for coating a flexible web with a coating material which is sensitive to and broken by a strong pressure.

The most prominent feature of the coating apparatus in accordance with the present invention is that the coating material can be applied on a flexible web running at a high speed under stable conditions to form a uniform layer of coating thereon.

In order to accomplish the above objects, the coating apparatus in accordance with the present invention utilizes air pressure causing the web to be pressed lightly against the coating roll. Therefore, in accordance with the present invention, it is possible to apply the coating material at a constant thickness without destroying the properties of the coating material. Further, it is possible to apply the coating material uniformly on the web without scratching the surface of the web or without making wrinkles in or causing slack in the web. It will be also understood that the application of the coating material on the web can be performed at a low. cost in accordance with this invention. Further, since the application of the coating material to the web can be performed stably in a constant thickness even if the thickness of the web is not uniform.

As apparent from the above description, the coating apparatus in accordance with the present invention is applicable ito various technical areas such as paper manufacture, photographic film manufacture, any kind of copying paper manufacture, plastic sheet film manufacture, textileindustries and so forth, in which various kinds of coating material are applied on a continuously travelling web.

These and other objects, features and advantages of the invention will be apparent from the following detailed description of the preferred embodiments thereof taken in conjunction with the accompanying drawing hereinbelow described.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view showing the arrangement of the web coating apparatus in accordance with the present invention,

, FIG. 2 is a schematic sectional side view showing the main portion of the web coating apparatus in accordance with an embodiment of the present invention,

,FIG. 3 is a schematic sectional front view of a main portion of the web coating apparatus as shown in FIG.

FIG. 4 is a sectional side view showing another embodiment of the coating apparatus in accordance with the present invention,

FIG. 5 is a sectional front view of the apparatus shown in FIG. 4,

7 FIG 6 is a sectional side view showing still'another embodiment of the coating apparatus in accordance with the present invention,

FIG. 7 is a sectional front view of the apparatus shown inFIG. 6, I

FIG. 8 is a sectional side view showing a further embodiment of the coating apparatus in accordance with the present invention,

' FIG. 9 is a sectional front view of the apparatus shown in FIG. 8, and

FIG. 10 is a schematic sectional side view of a main portion of the web coating apparatus in accordance with a still further embodiment of the present invention showing an application thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Now referring to FIG. 1 showing the arrangement of the coating apparatus in accordance with the present invention, the reference numeral 1 indicates a flexible web such as paper, film and the like travelling continuously in the longitudinal direction along a press roll 2, a coating roll 3 and a backing roll 7. The web I is pressed lightly on the periphery of the coating roll 3 by the tension made by the press roll 2 and the backing roll 7. The coating roll 3 is partly immersed in a coating material 5 contained a reservoir 4 so that the surface of the coating roll 3 may carry the coating material 5 thereon upward when it rotates about its axis. The backing roll 7 serves to feed the web 1 therearound by contacting the back surface thereof and hold the web 1 against the air flow ejected from an air doctor 6 which in turn scrapes off the excessive amount of coating material on the web 1 and makes the surface of the coating layer smooth. Reference numeral 8 indicates an air box or air chamber located close to the web on the coating roll 3, there being a slight space between the air box 8 and the back surface of the web 1. The air box 8 is supplied with an air flow to provide a-static air pressure on the backside of the travelling web 1. Reference numeral 9 indicates a duct for supplying the air flow'from a high pressure fan or blower 10.

Referring now to FIGS. 2 and 3 showing the internal construction of the air chamber 2, high pressure air sent from a blower, not shown, passes through the ducts 9 and enters into a cylindrical filter 12 from both ends thereof through a pair of duct guides 11 and 11' connected at the opposite ends of the cylindrical filter 12. Cylindrical filter 12 is arranged laterally with the coating roll 3 with its central axis parallel to the axis of revolution of the rll3. The cylindrical filter 12 is covered by air chamber 8 and an air space 13 is defined around the cylindrical filter 12 on the surface of the coating roll 3. The pressurized air sent into the cylindrical filter l2 flows out of the filter 12 through the filter wall thereof and is filtered thereby, and the pressurized air fills air space 13 to maintain a static air pressure in the air space 13. This air pressure holds the running web in good contact with the surface of the coating roll 3 and escapes away through a small space formed betweenthe surface of the web and the lower end of the air chamber 8.

Referring to FIGS. 4 and showing another embodiment of the present invention, pressurized air sent from a blower, not shown, through ducts 9 is introduced into the filter having a cylindrical configuration by way of a pair of duct guides 11, 11' similar to the apparatus shown in FIGS. 2 and 3. The pressurized air sent into the cylindrical filter 12 flows out of the filter l2 and fills the air space 13. The air space 13 is defined by a pair of side walls and an upper plate and a lower bottom plate having a pair of openings, such as slits or a plurality of holes, 15 and 16 on the both sides thereof. Openings l5 and 16 extend parallel to the axis of revolution of the coating roll 3 and a bottom plate 14 is provided between the openings 15 and 16. A static air pressure is generated between the bottom plate 14 and the surface of the web 1, with the pressure holding the web I in firm and stable contact with the surface of the coating roll 3. Similar elements in the different embodiments are all indicated using the same reference numerals, and accordingly, the description of the similar parts of the embodiments hereinafter described to those of the embodiment hereinbefore described will be omitted where possible to simplify the description of the embodiments.

Now referring to FIGS. 6 and 7 showing a third embodiment of the present invention, under the cylindrical filter 12 similar to that shown in the foregoing embodiments is provided a lateral slit 31 formed between a pair of plates 17 and 18 having openings such as slits or a plurality of holes laterally extending to confine an air chamber around the cylindrical chamber 12 and form a lateral opening 31 thereunder in parallel relationship thereto. Further, under opening 31 thin membranes l9 and 20, with a small slit or holes 21 are provided. The membranes l9 and 20 are flexible and thin so that the air pressure may push the membranes l9 and 20 towards the back surface of the web 1 and the dynamic air pressure created by air flow between the membranes l9 and 20 will press lightly against web 1 together with the static air pressure generated by the air flowing out of the slit 21 thereof. Thus, web 1 is pressed lightly against the surface of the coating roll 3 and the coating material 5 contained in the reservior 4 and carried on the; surface of the coating roll 3 is well applied onto the surface of the flexible web 1. The flexible membranes l9 and 20 can be of a flexible material such as polyethylene film, vinyl chloride film, other high molecular weight films, cotton cloth, linen cloth, silk cloth, other textile cloths, rubber film and so forth.

Now referring to FIGS. 8 and 9 showing the fourth embodiment of the present invention, an air chamber 22 is connected with a pair of ducts 9 and 9" through a pair of duct guides 1 l and 11. The air chamber 22 is an elongated chamber extending laterally, parallel to the axis of the coating roll 3. The air chamber 22 has a narrow opening, such as a slit or a plurality of holes 23 at the bottom thereof extending close to the top of the coating roll 3 in parallel relationship thereto as shown in FIGS. 8 and 9. Coating roll 3 is provided just under the opening-23 with a slight space therebetween so that the air jet streaming out of the opening 23 can blow strongly against the back surface of the web 1 and the coating material 5 carried on the coating roll 3 can be sufficiently and stably transferred from the coating roll 3 to the surface of the running web 1.

Now referring to FIG. 10, showing a still further embodiment of the present invention, an air chamber 8 for blowing an air stream on the backside of the flexible web 1 is made movable for up and down motion. Air chamber 8 is provided=with openings 27, 28 and 29 such as slits or as a plurality of holes on the bottom plate 30 thereof, similar to the openings shown in the second embodiment described in FIGS. 4 and 5. Upstream of air chamber 8 is provided a lap roll 26 rotatably supported on a fixed shaft and downstream of the air chamber 8 is provided a backing roll 7 on a fixed shaft. The position of the lap roll 26 and the backing roll 7 is so selected that the web 1, tensioned therebetweeri, may not be in contact with the surface of the coating roll 3 when the air chamber 8 is out of the way of the web or retracted upward as indicated with a broken line 24 in FIG. 16. Web 1 is put into contact with the surface of the coating roll 3 when the air chamber 8 is moved downward to urge the web to be in contact therewith as indicated with a dot-and-dash line 25 in FIG. 10. Air chamber 8 is supplied with a pressurized air introduced thereto and air jet streams of openings 27, 28 and 29 push the web downward therewith. Thus, the web 1 is brought down, into contact with the surface of the coating roll 3 as shown in FIG. 10, and the coating material carried thereby is applied on the surface of the web 1. It is preferred in this embodiment that the position of the central slit 28 should be selected horizontally between the axis of the coating roll 3 and the edge of the reservoir 4 containing the coating material 5.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

What is claimed is:

1. In a web coating apparatus employing a coating roll and means for feeding the web into contact with the coating roll periphery which carries a coating material thereon, the improvement comprising:

means defining an air chamber overlying the back of the web at the position where the web is in contact with the coating roll, air blowing means for pressurizing said air chamber, said air chamber being provided with a flexible membrane which directly overlies the back of the web, said flexible membrane being provided with at least one lateral opening parallel to the axis of the coating roll such that said flexible membrane flexes under static air pressure within said air chamber towards the back of said web but does not contact the back of said web, I

and wherein, air escaping from said chamber between said flexible membrane and said web acts to form dyanmic air pressure means therebetween and wherein said opening within said flexible membrane directly applies static air pressure against said web.

2. The web coating apparatus as claimed in claim 1, wherein said air chamber further comprises a plate facing said web and having at least one opening therein parallel to and in alignment with the opening within I said flexible membrane, said plate being positioned to the side of said flexible membrane opposite that of said web.

3. The web coating apparatus as claimed in claim 1, wherein said opening within said flexible membrane comprises a slit extending at least the width of said web.

4. The web coating apparatus as claimed in claim 1, wherein said membrane comprises a flexible film.

5. In a web coating apparatus employing a coating roll and means for feeding the web into contact with the coating roll periphery which carries a coating material thereon, the improvement comprising:

a backing roll and a lap roll positioned on opposite sides of said coating roll with said web in running contact therewith and under tension, said lap roll and said backing roll being positioned such that said tension web is normally spaced from the periphery of said coating roll,

an air chamber overlying the back of said web and being movable towards said web to press said web against the periphery of said coating roll, said air chamber including a bottom plate and having a plurality of spaced, laterally extending openings parallel to the axis of rotation of said coating roll,

pressurized air generating means coupled to said air chamber for pressurizing said chamber such that said pressurized air passing through said openings of said bottom plate presses the back of said web against said coating roll periphery, and

wherein the openings within the bottom plate of said air chamber are three in number and comprise parallel, lateral slits with the central slit being upstream of the axis of rotation of the coating roll. 

1. In a web coating apparatus employing a coating roll and means for feeding the web into contact with the coating roll periphery which carries a coating material thereon, the improvement comprising: means defining an air chamber overlying the back of the web at the position where the web is in contact with the coating roll, air blowing means for pressurizing said air chamber, said air chamber being provided with a flexible membrane which directly overlies the back of the web, said flexible membrane being provided with at least one lateral opening parallel to the axis of the coating roll such that said flexible membrane flexes under static air pressure within said air chamber towards the back of said web but does not contact the back of said web, and wherein, air escaping from said chamber between said flexible membrane and said web acts to form dyanmic air pressure means therebetween and wherein said opening within said flexible membrane directly applies static air pressure against said web.
 2. The web coating apparatus as claimed in claim 1, wherein said air cHamber further comprises a plate facing said web and having at least one opening therein parallel to and in alignment with the opening within said flexible membrane, said plate being positioned to the side of said flexible membrane opposite that of said web.
 3. The web coating apparatus as claimed in claim 1, wherein said opening within said flexible membrane comprises a slit extending at least the width of said web.
 4. The web coating apparatus as claimed in claim 1, wherein said membrane comprises a flexible film.
 5. In a web coating apparatus employing a coating roll and means for feeding the web into contact with the coating roll periphery which carries a coating material thereon, the improvement comprising: a backing roll and a lap roll positioned on opposite sides of said coating roll with said web in running contact therewith and under tension, said lap roll and said backing roll being positioned such that said tension web is normally spaced from the periphery of said coating roll, an air chamber overlying the back of said web and being movable towards said web to press said web against the periphery of said coating roll, said air chamber including a bottom plate and having a plurality of spaced, laterally extending openings parallel to the axis of rotation of said coating roll, pressurized air generating means coupled to said air chamber for pressurizing said chamber such that said pressurized air passing through said openings of said bottom plate presses the back of said web against said coating roll periphery, and wherein the openings within the bottom plate of said air chamber are three in number and comprise parallel, lateral slits with the central slit being upstream of the axis of rotation of the coating roll. 